1. Field of the Invention
The present invention relates to polymer dispersions having a Brookfield viscosity of less than 10,000 cps. at 25.degree. C. More particularly, the invention relates to polymer dispersions particularly useful in the preparation of polyurethane foams which dispersions are prepared by blending a hydroxy-containing finely divided solid polymer with a polyol. The hydroxy-containing solid polymer is prepared by polymerizing in the presence of a free radical catalyst and an organic solvent a major amount of an ethylenically unsaturated monomer or mixture of monomers and a minor amount of a hydroxy-terminated organic compound having from one to eight hydroxyl groups, an equivalent weight of from 500 to 10,000 and containing a polymerizable carbon-to-carbon double bond.
2. Prior Art
The preparation of graft polymer dispersions from vinyl monomers and unsaturation-containing polyether polyols and the use thereof in the preparation of polyurethane compositions is well known in the art, as evidenced by U.S. Pat. No. 3,652,639 and Great Britain Pat. No. 1,126,025. These patents disclose various methods of preparing the dispersions. Illustrated therein is the fact that as the amount of vinyl monomer exceeds twenty percent by weight of the dispersion, the viscosity of the dispersion greatly increases, thus restricting the handling and use of the dispersions. Since it is primarily the polymeric species derived from the polymerization of the vinyl monomer(s) and the unsaturation-containing polyether polyol which provide the improved physical properties to the polyurethane compositions, it is of course desirable to increase the vinyl monomer content of the graft polymer dispersions. Prior to the subject invention, such efforts have been largely unsuccessful because of the viscosity problems mentioned above.